'UP UNTIL NOW, it's been about how much print you can wear," said Mary Katrantzou, the London designer known for her wildly inventive and usually wildly hued prints. Ms. Katrantzou was talking about the clashing, pile-it-on, head-to-toe looks popular on street-style blogs.

But this season, the best motifs take a much quieter approach. As the screams of neon yellow and fluorescent fuchsia from previous seasons fade like a summer tan, they're being replaced by darkly romantic floral motifs—sometimes evoking film noir, sometimes a bit punk-tinged—which are usually most stylish worn in moderation.

Though Ms. Katrantzou's fall prints aren't technically florals, they reference the natural world with melancholy landscapes of leafless trees, in icy gray and silver. "It isn't the season to go all bright," she added.

However, even designers who kept a fully bloomed rose in their bouquet did so with a somber and edgy twist. Milan-based Massimo Giorgetti wanted to shatter the classic floral for the fall collection of his print-heavy label MSGM. He sliced classic photographs of roses into sharp fragments and set them against a midnight blue background to create a pattern he described as "romantic punk rocker." "There was a punk mood in the air with the Met Ball," Mr. Giorgetti explained, referring to the opening gala of this year's "Punk: Chaos to Couture" exhibit at New York's Costume Institute.

It's not surprising, then, that Givenchy designer Riccardo Tisci, who was one of the gala's co-hosts and whose label was one of the sponsors of the show, also infused his fall collection with moody blooms. He collaged his prints into gypsy-inspired looks, cross-pollinated with tough elements like black leather and grunge-y plaids. A black wool motorcycle jacket was printed with curving floral illustrations. Also in the punk vein, Saint Laurent designer Hedi Slimane showed dark floral baby-doll dresses that were a homage to rock-chick icons like Courtney Love and other Riot Grrrls of the 1990s.

For something more demure, less mosh-pit, look to Valentino's embroidered dresses and Lanvin's rose jacquard cocktail frocks. Or to Louis Vuitton's muted satin coats and skirts dotted with tiny flowers, shown on a runway set that looked like a shadowy, film-noir hotel interior.

Unlike some trends, this one intuitively makes sense. As days grow short, we naturally gravitate to darker, more polished fare. "Fluorescent, I'm sick of it, and it's a summer thing," said Mr. Giorgetti. "It doesn't work for winter."

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